1. Field of the Invention
The present invention relates to a method for automatically sheathing goods, e.g. lumber, in plastic bags and, more particularly, in a plastic tube which is expanded for receiving the material and which is then sealed.
2. Description of the Prior Art
The forest industry is confronted with storage and exportation problems in that wood products, for instance lumber pieces, which result from milling operations and which are ready for commercial use must be stored in dry locations such as to preserve therein an appropriate degree of humidity (e.g. 6.0% to 8.0%) and must further be stored in dark settings such as to prevent the wood products from being exposed to ultraviolet rays (i.e. UV rays)
Bagging or sheathing apparatuses have been extensively used to bag agricultural products, for example hay bales, directly in the field or on the farm land and various such known apparatuses can be found in the prior art. Indeed, bagging devices are described, for instance, in U.S. Pat. No. 5,425,221 which issued to Pronovost et al. on Jun. 20, 1995 and in U.S. Pat. No. 5,398,487 and No. 5,421,144 which issued to Inmam et al. on Mar. 21, 1995 and on Jun. 6, 1995, respectively. These sheathing apparatuses provided extendable arms which are arranged to radially stretch a resilient cylindrical sheath, i.e. a plastic tube, such as to increase the transverse or cross sectional dimensions of the opening thereof thereby facilitating the insertion of hay bales within the tubular sheath. Once the material to be bagged is properly received in the sheath, the arms are retracted to allow the sheath to return under its inherent resiliency to a more contracted state and thus tightly envelop the bales.
More particularly, the above prior art apparatuses typically comprise the following basic elements: a rigid frame which is fixedly mounted on the chassis of a vehicle capable of displacement along the ground, a plurality of sheath retaining hook members which are mounted on the rigid frame and which are capable of outward and inward radial movements with respect to the rigid frame, and stretchable tubular bags. Each hook member is operated by its individual hydraulic ram. The tubular sheaths are normally disposed in a pleated, accordion-like, folded state and are gradually unfolded as material is received therein for bagging purposes. With the above apparatuses, the folded sheaths need to be manually positioned on the hook members. Also, the end pleat of the sheath must be pulled off the hook members to facilitate gathering and tying of sheath material to close the end of the sheath, i.e. of the formed bag. Therefore, the tubular sheath which is folded with accordion pleats around the hook members will gradually unfold during the loading of successive bales within the sheath so as to tighten around the loaded bales once the sheath is allowed to contract.
Basically, all of the above bale sheathing apparatuses are intended for sheathing agricultural products such as grass, hay, stalks and the like, into an elongated plastic bag having elastic characteristics and are thus not well adapted for bagging heavy rectangular loads, such as bundles of lumber strips, planks, boards, etc.